This disclosure relates to planetary gear systems, and, more particularly, to a planet gear having a damping element (elastomeric isolator) that reduces energy (vibration and noise) propagation during the operation of a planetary gear system into which the planet gear is incorporated.
Planetary gear systems typically comprise a plurality of drivable or idler gears (e.g., planet gears) engaged by a pinion (e.g., a sun gear). Because they share a single load between several meshes of gears, planetary gear systems are generally more compact than parallel shaft drives and offer significant space savings. Planetary gear systems do, however, produce audible noise that may be a detractor in some applications.
The problem of audible noise is exacerbated as a result of two conditions that exist within known planetary gear systems. The first condition is a function of the material of fabrication of the gears. Typically, at least one of the gears is fabricated from metal. Metal gears provide a harsher impact of the surfaces of the gear teeth when the gears mesh during the operation of the system. Such a reduced compliant impact increases the amount of noise generated. The second condition is a function of the damping aspects of the system. Elastomeric O-rings may be disposed between an inside surface of a bored planet gear tooth portion and an outside surface of a hub to minimize the transfer of gear mesh energy (vibration) from the teeth of the gear to the hub and isolate the vibration from the remainder of the system, thereby reducing audible noise. Conventional elastomeric O-rings, however, have a radial stiffness that is too high to isolate all of the gear mesh energy from propagating to other parts of the gear system when the planet gear tooth portion compresses the O-rings against the hub after assembling a planet gear. Therefore, an isolator with a design that retains an effective spring rate to isolate gear mesh energy is needed that is cost effective when assembling a planet gear in which an elastomeric isolator is compressed between the inside surface of an axially bored planet gear and the outside surface of a hub.
An elastomeric isolator for use with a planet gear in a planetary gear system is disposed between the structural components of the planet gear. The planet gear includes a toothed portion having an axial bore, a hub coaxially orientable within the axial bore such that a space is defined between the hub and the toothed portion, and an elastomeric isolator disposed therebetween. The elastomeric isolator is configured having a ring having a first dimension interconnecting a plurality of spheroids having a second dimension for retaining the spring rate of the ring. The configuration of the elastomeric isolator, in conjunction with the architecture of the planet gear, provides for a radial spring rate and a radial damping ability that effectively minimizes the amount of gear mesh energy transferred to other elements of the planetary gear system.